IPs and Nameservers

I have a few people on my reseller server wanting their own dedicated IPs and private nameservers. I tried setting this up in Reseller Center but I don't have the IPs to do it. How can I get more IPs? I know there is an option in the server's WHM for setting up more IPs but it doesn't make sense to me at all.
Anyone able to provide some advice or help?
Thanks in advance.